Knowledge and expertise in both photobiology and immunology will be combined to explore the effects of ultraviolet radiation on the immune system. A major objective of this proposal is that the results of careful comparison studies utilizing a range of wavebands of radiation alone and with the addition of 8-methoxypsoralen in several model systems will provide a perspective of photoimmunology. The in vitro model will be used to explore the effects of radiation on the viability and function of lymphocytes as indicated by the response of those cells to mitogens and their ability to exclude dyes. Unscheduled DNA synthesis by the cells will be examined after exposure to radiation to study a possible mechanism of radiation-induced damage. In the animal model, the influence of radiation on cell-mediated responses to a contact sensitizer, an intradermal antigen and allografts will be studied while the humoral response to the intradermal antigens will also be monitored. In vivo studies in normal human subjects will examine the effects of UVB and psoralen/UVA radiation on the function and viability of peripheral blood lymphocytes by assessing the response of the cells to mitogens and the distribution of T cells, B cells and sub-populations of T cells. The mechanism of alterations observed in E rosette-forming cells will be explored to distinguish between a direct effect radiation on cells and on indirect effect via an inflammatory mediator or photoproduct released by the incident radiation and also to assess the reversibility of the alterations. The possibility that exposure of patients with psoriasis to therapeutic radiation may be harmful via an effect on immune function will be further studied by examining the effect of UVB phototherapy on the distribution of T and B lymphocytes and the response of these cells to mitogens; the ANA response in psoriatic patients during both UVB and psoralen/UVA therapy will also be studied. Finally, the influence of PUVA on immune function in patients with atopic eczema will be explored by monitoring in vivo responses to antigens, serum IgE levels, the distribution of T and B lymphocytes in peripheral blood and the response of these cells to mitogens and antigens before, during and after a course of PUVA therapy.